Area separation firewall system

ABSTRACT

A firewall includes wallboard arranged in three or more layers. The wallboard may include gypsum, fiber glass, and/or vermiculite. The firewall may be reinforced with fasteners, such as laminating screws, affixing the layers of wallboard to one another. The firewall may be incorporated into an area separation wall such that the area separation wall satisfies the standards of ASTM E119 or UL 263.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims benefit of U.S. Provisional PatentApplication No. 63/262,268 filed Oct. 8, 2021, titled “AREA SEPARATIONFIREWALL SYSTEM,” which is incorporated herein by reference in itsentirety.

FIELD OF THE DISCLOSURE

The present disclosure relates to area separation firewalls. Moreparticularly, the disclosure relates to an improved firewall for use inarea separation firewall systems, with this system including wider,thinner pieces of gypsum wallboard that are easier to manufacture andinstall as compared to traditional 1″ thick shaft liner wallboard.

BACKGROUND

International, state, regional and local building codes require thatmulti-family residential buildings include certain fire protectionfeatures, such as firewalls between residential units. The standard forqualifying fire rated systems is either ASTM E119 (“Standard TestMethods for Fire Tests of Building Construction and Materials”) orANSI/UL 263 test (“the Standard for Safety of Fire Tests of BuildingConstruction Materials”). During this testing, an area separationfirewall system therein is heated to 1000° F. and then ramped to 2000°F. The firewall must be able to resist this heat for a specified periodof time, such as two hours. Another aspect of this testing is a hosestream test, wherein a pressurized stream of water is directed at thevertical fire resistive wall assembly after fire endurance exposuresimulating a fire being extinguished. The vertical firewall must be ableto maintain its structural integrity, and not allow water to passthrough it.

For decades, multi-family residential firewalls have been constructedwith two pieces of 1″ thick shaft liner wallboard. These wallboardpanels are particularly difficult to manufacture and typically slowsproduction by a factor of two or more. These thick pieces of wallboardare also cumbersome and only 2′ wide—as compared with a 4′ width forother wallboard panels—in order to manage the weight thereof. Thisdecreased width translates to added materials and labor when installingthe firewall, since the 2 pieces of shaft liner wallboard must be joinedwith the next section using a metal H-Stud. Despite the long tenure ofthese firewalls, little improvement has been made to the conventionaldesign. As such, there remains a great need for an improved firewallwallboard that can be efficiently manufactured and installed.

BRIEF DESCRIPTION OF THE DRAWINGS

Various embodiments of the present disclosure will be understood morefully from the detailed description given below and from theaccompanying drawings. In the drawings, like reference numbers mayindicate identical or functionally similar elements. Embodiments aredescribed in detail hereinafter with reference to the accompanyingfigures, in which:

FIG. 1 is a top view of a prior art area separation firewall.

FIG. 2 is a top view of an area separation firewall according to anembodiment of the present disclosure.

FIG. 3 is a side view of an area separation firewall according to anembodiment of the present disclosure.

FIG. 4 is a side view of an area separation firewall according toanother embodiment of the present disclosure.

FIG. 5 is an opposite side view of the area separation firewall of FIG.3 or FIG. 4 .

FIG. 6 is a cross-sectional side view of an area separation firewallwithin an intermediate floor intersection according to an embodiment ofthe present disclosure.

FIG. 7 is a cross-sectional side view of an area separation firewall ata roof junction according to an embodiment of the present disclosure.

FIG. 8 is a cross-sectional top view of an area separation firewall atan exterior wall intersection according to an embodiment of the presentdisclosure.

FIG. 9 is a graph showing the results of Example 1.

FIG. 10 is a graph showing the results of Example 2.

DETAILED DESCRIPTION

The following disclosure provides many different embodiments orexamples. Specific examples of components and arrangements are describedbelow to simplify the present disclosure. These are, of course, merelyexamples and are not intended to be limiting. In addition, the presentdisclosure may repeat reference numerals and/or letters in the variousexamples. This repetition is for the purpose of simplicity and clarityand does not in itself dictate a relationship between the variousembodiments and/or configurations discussed.

FIG. 1 is a top view of a conventional 2-hour area separation firewall.The area separation firewall includes a pair of opposite interior walls5 each supported on a series of studs 4, which are typically made ofwood. Between the interior walls 5 is a firewall 8 spaced from the studs4 by an airgap 7, which may be about ¾″. The firewall 8 includestwo-wallboard-thick panels comprising two, 1″ thick wallboards 3. Eachwallboard 3 may have a width W₀ of about 2′. The panels of the firewall8 are joined together by H-studs 2 and an end panel of the firewall 8 iscapped with a C-stud 1. The C-studs 1 and H-studs 2 may be made ofmetal, such as steel. The H-studs are fixed to wood framing via clips 6,which are typically made from aluminum and configured to break away ifthe wood framing collapses in a fire thereby leaving the firewall 8standing.

FIG. 2 is a top view of a 2-hour area separation firewall 100 accordingto an embodiment of the present disclosure. The area separation firewall100 includes a pair of opposite interior walls 50 each supported on aseries of studs (framing) 40, which are typically made of wood or metal.The studs 40 are separated by a maximum distance W₂ of about 2′. Betweenthe interior walls 50 is a firewall 80 spaced from the studs 40 by anairgap 70 of a minimum of ¾″. The firewall 80 includesfour-wallboard-thick panels comprising four wallboards 30 each having anominal thickness of, e.g., less than 1″ or about 0.5″. Accordingly, thefirewall 80 may be about as thick as a traditional firewall having two1″ thick pieces of wallboard. Each wallboard 30 may have a width W₁ ofabout 2′, greater than 2′, about 3′, about 3.5′, about 4′, greater than4′, about 54″, or at most 54″. The increased width of the wallboards 30is made possible due to the thinner profile, whereby the wallboards 30may be about as heavy as traditional firewall wallboards. The panels ofthe firewall 80 are joined together by H-studs 20 and an end panel ofthe firewall 80 is capped with a C-stud 10, such as a 2″ C-stud. Thefirewall 80 may be friction fit into each of the C-studs 10 and H-studs20. The H-studs 20 and/or C-studs 10 may be attached to the wood framing40 with aluminum clips 60. In some embodiments, the clips 60 are madefrom aluminum and designed to melt or break away if the wood framing 40collapses in a fire thereby leaving the firewall 80 standing.

In any embodiment, the material used for the wallboard 30 is typicallymore fire resistant than that used for the interior walls 50. In someembodiments, the wallboard 30 may be comprised of gypsum, fiber glass,and vermiculite. In one or more embodiments, the wallboard 30 comprisesone or more of a dispersant, a fire retardant (retarder), a chelatingagent, a soap, a binder or adhesive, an accelerator, a surfactant, anacid, a stabilizing agent, and/or a foaming agent. In some embodiments,the dispersant may include polynaphthalene sulfonate in a sodium orcalcium salt solution (having 2-80% solids content). In someembodiments, the binder or adhesive may include starch, such asacid-modified corn starch (AMCS) or pre-gelatinized corn starch. In someembodiments, the retarder or chelating agent may include pentasodiumdiethylenetriaminepentaacetate. In some embodiments, the acid mayinclude boric acid. In some embodiments, the stabilizing agent is sodiumtrimetaphosphate (STMP). In some embodiments, the soap, surfactant,and/or foaming agent may include ammonium alkyl ether sulfate. In oneembodiments, the wallboard may have the following formulation:

TABLE 1 Component Content (lbs./msf) Retarder 0.02-4.0  Stucco 1300-1700Soap 1.0-7.0 Starch  3.0-12.0 Vermiculite 25.0-65.0 Fiber glass 3.0-16.0 Core adhesive  6.0-25.0 Dispersing agent 1.0-8.0 Foaming agent0.01-5.0  Boric acid 0.02-5.0  STMP 1.50-9.0  Accelerator  6.0-15.0Average Weight 1950-2100

In one or more embodiments, the wallboard 30 may be a commerciallyavailable wallboard from American Gypsum sold under the tradenameM-BLOC® Ekcel™ TYPE X. In one or more embodiments, the wallboard 30 doesnot include asbestos and/or does not include detectable levels offormaldehyde. Since the firewall 80 is usually installed prior to thecompletion of the roof and exterior walls, the wallboards 30 may beexposed to the elements for a period of time. As such, in someembodiments, an exterior surface of the wallboard 30 may be wrapped in amold and moisture resistant covering. In some embodiments, the mold andmoisture resistant covering may be one that has scored at least a 8, 9or 10 under the ASTM D3273 (Standard Test Method for Resistance toGrowth of Mold on the Surface of Interior Coatings in an EnvironmentalChamber). In some embodiments, coverings, such as the mold and moistureresistance covering discussed above, may cover the face and back of thewallboard 30. In some embodiments, the coverings comprise a paper or aglass mat.

In some embodiments, the interior walls 50 may be formed from ½″ or ⅝″thick gypsum board available from American Gypsum under the tradenamesLIGHTROC® or CLASSICROC® or any other fire rated or non-fire ratedwallboard panel.

Turning to FIG. 3 , each four-wallboard-thick panel may be supported atthe top and bottom thereof with a C-Runner channel 12. The pieces ofwallboard 30 each have a height H₄ that corresponds to the height of theH-stud 20 in use. In some embodiments, the height H₄ may be up to 8′, upto 10′, up to 12′, up to 14′ or up to 16′. As will be described in moredetail below, the area separation firewall 100 will typically extendthrough all floors of the building and therefore will have a height thatis generally equivalent to the height of the building. In order toprovide additional support to the wallboards 30, fasteners 94 may byinstalled to fasten the four layers of wallboard 30 to one another. Insome embodiments, the fasteners 94 are nails, screws, or an adhesive. Insome embodiments, the fasteners 94 are 1½″ Type G laminating screws. Insome embodiments, the fasteners 94 are long enough to penetrate throughone, two, or three layers of wallboard 30. In some embodiments, thefasteners 94 are shorter than a thickness of the firewall 80 so that thefasteners 94 do not protrude out of the firewall 80. In someembodiments, the fasteners 94 are greater than ½ the thickness of thefirewall 80 such that fasteners 94 installed on opposite sides of thefirewall 80 are capable of laminating the layers of wallboard 30 to eachother.

When the fasteners 94 are employed, they may be configured in a randomassortment or they may be configured in a pattern 90. In the embodimentshown in FIG. 3 , the fasteners 94 are equally spaced from each otherwithin the pattern 90 and the pattern 90 is spaced from the edges of thewallboard 30. In particular, within the pattern 90, the fasteners 94 arespaced by a lateral distance D₂ and a vertical distance H₂. Thedistances D₂ and H₂ may be the same or different. In some embodiments,the distance D₂ is less than the distance H₂. In other embodiments, thedistance D₂ is greater than the distance H₂. The pattern 90 is spacedfrom the vertical edges of the wallboard 30 by distances D₁ and D₃,which may be the same or different. In some embodiments, one or both ofthe distances D₁ and D₃ is the same as the distance D₂. The pattern 90is spaced from horizontal edges of the wallboard 30 by distances H₁ andH₃, which may be the same or different. In some embodiments, thedistances D₁, D₂, D₃, H₁, H₂, and H₃ are each independently from about3″ to about 36″, from about 6″ to about 24″, from about 12″ to about30″, from about 20″ to about 36″, about 16″, about 24″, or about 12″.

With reference to FIG. 4 , an alternative pattern 90A is shown. In FIG.4 , the pattern 90A is spaced from the edges of the wallboard 30 bydistances D₄ and D₇, which may be the same or different from oneanother. The pattern 90A includes a middle column of fasteners 94 spacedfrom the outer columns of fasteners 94 by distances D₅ and D₆, which maybe the same or different from one another. In some embodiments, thedistances D₄, D₅, D₆, and D₇ are each independently from about 3″ toabout 36″, from about 6″ to about 24″, from about 12″ to about 30″, fromabout 20″ to about 36″, about 16″, about 24″, or about 12″.

Turning to FIG. 5 , an opposite side of the wallboard 30 panel may alsoinclude a set of fasteners 94. In some embodiments, the fasteners 94 arearranged in a second pattern 92, which may be the same or different fromthe pattern 90. In FIG. 5 , the pattern 92 is distinct from, butcomplementary to, the pattern 90. Arranging the fasteners 94 in thismanner provides excellent structural support while conserving materials.The fasteners 94 are spaced from one another within the pattern 92 by alateral distance D₉ and a vertical distance H₂. Although the embodimentshown includes the same vertical spacing for patterns 90 and 92, therespective vertical spacings may be, for example, offset by a distanceof about 3″, about 6″, about 9″, or about 12″. In some embodiments, thedistance D₉ is greater than the distance D₂. In other embodiments, thedistance D₉ is less than the distance D₂. In yet other embodiments, thedistance D₉ is equal to the distance D₂. The pattern 92 is spaced fromthe vertical edges of the wallboard 30 by distances D₈ and D₁₀, whichmay be the same or different. In some embodiments, one or both of thedistances D₈ and D₁₀ is the same as the distance D₉. In someembodiments, the distances D₈, D₉, and D₁₀ are each independently fromabout 3″ to about 36″, from about 6″ to about 24″, from about 12″ toabout 30″, from about 20″ to about 36″, about 16″, about 24″, or about12″. In an embodiment, the distance D₁ is about 12″, the distance D₂ isabout 24″, the distance D₃ is about 12″, the distance D₄ is about 12″,the distance D₅ is about 12″, the distance D₆ is about 12″, the distanceD₇ is about 12″, the distance D₈ is about 16″, the distance D₉ is about16″, the distance D₁₀ is about 16″, the distance H₁ is about 12″, thedistance H₂ is about 24″, the distance H₃ is about 12″, and the distanceH₄ is about 10′.

In any of the above embodiments, the fasteners 94 may be spaced suchthat any one fastener 94 has at least one adjacent fastener 94 within aset maximum distance. The at least one adjacent fastener 94 may be onthe same side of the firewall 80 as the any one fastener 94 or mayinclude fasteners 94 on the opposite side of the firewall 80. In someembodiments, the set maximum distance is from about 6″ to about 24″,about 8″, about 12″, about 14″, about 16″, about 18″, about 20″, about22″, or about 24″.

With reference to FIG. 6 , in multi-level buildings, the area separationfirewall 100 may need to traverse an intermediate floor junction. Asshown, an airgap 70 is maintained along an entire length of the areaseparation firewall 100. In some embodiments, an additional fireblocking material 32 may be required proximate the floor joists 46. Thefire blocking material 32 may comprise, for example, gypsum wallboard(such as that described for wallboard 30) or a mineral or glass fiberinsulation. Insulation 48, such as glass fiber batt, may be placed asneeded between the interior walls 50. Between levels 80 a and 80 b ofthe firewall 80, two C-studs 10 may be positioned back-to-back. Althoughthe junction (at C-studs 10) between levels 80 a and 80 b is shown at aposition above the upper floor 52 a, the junction may be between thefloor 52 a and ceiling 52 b or below the ceiling 52 b. In someembodiments, caulk or another sealant may be used at the junctionbetween C-studs 10 to create a smoke-tight joint.

Next, turning to FIG. 7 , the area separation firewall 100 is shown at ajunction with a roof deck 56. The roof deck 56 includes roofing 56 a. Insome embodiments, a layer 54 is needed below the roof deck 56, whereinthe layer 54 may be, for example, a layer of wallboard such as thatdescribed above. In some embodiments, the layer 54 is about ⅝″ thick. AC-stud 10 may cap the firewall 80 where it meets the roof deck 56. Atthis juncture, caulk or another sealant may be used to create asmoke-tight joint. In some embodiments, an additional fire blockingmaterial 32 may be required proximate the framing 44 (including ceilingjoists). The fire blocking material 32 may be as described above.

With reference to FIG. 8 , the area separation firewall 100 is shown ata junction with an exterior wall 58. In some embodiments, a sheathinglayer 48 may be included inside of the exterior wall 58. In someembodiments, the sheathing layer 48 is about ⅝″ thick. A C-stud 10 maycap the firewall 80 where it meets the sheathing layer 48 or theexterior wall 58. At this juncture, caulk or another sealant 12 may beused to create a smoke-tight joint.

Although the firewall 80 is described herein as comprising four piecesof wallboard 30, the firewall may include, for example, three, five, orsix pieces of wallboard 30. In any embodiment, the thickness of thefirewall 80 may be maintained at, for example, approximately 2″ byappropriately adjusting the thickness of the wallboard 30. For example,three pieces of wallboard 30 may each have a thickness of about ⅔″.

According to embodiments of the present disclosure, the firewall 80 mayprovide similar or improved fire protection as compared withconventional firewalls while significantly decreasing the cost ofproduction and installation. As discussed above, conventional 1″ thick,2′ wide wallboard can slow production by a factor of two or more.Conversely, the wallboard 30 disclosed herein does not cause suchreduction of production. Additionally, even though four pieces ofwallboard 30 are used for each panel (as compared to two in conventionalfirewalls) and fasteners 94 may be required, installation of thefirewall 80 of the present disclosure is still faster than that ofconventional firewalls. This is primarily because the wider pieces ofwallboard 30 result in fewer H-studs 20 being required.

EXAMPLES Example 1

An area separation firewall generally as shown in FIG. 2 was assembledusing four pieces of ½″ thick wallboard for the firewall, type Glaminating screws as fasteners for the wallboard, steel H-studs, steelC-studs, wood studs spaced at 16″, glass fiber insulation batts frictionfitted into cavities between the wood studs, and regular ½″ thick gypsumwallboard secured to the wood studs for the interior walls. Thisassembly was then tested according to standard ASTM E90-09 (2016):Laboratory Measurement of Airborne Sound Transmission of BuildingPartitions and Elements. The results of this test are shown in FIG. 9 ,wherein the Sound Transmission Class (STC) contour is shown as a doubleline, the transmission loss (TL) is shown as a single line, and the STCdeficiencies are shown as a bar graph. This test resulted in an STCrating of 56, which corresponds to the STC contour shown.

Example 2

An area separation wall was assembled as described in Example 1, exceptthat the wood studs were spaced at 24″ o/c. This assembly was thentested according to standard ASTM E90-09 (2016). The results of thistest are shown in FIG. 10 . This test resulted in an STC rating of 61,which corresponds to the STC contour shown.

Example 3

An area separation wall was assembled as described in Example 2. Thisassembly was then tested according to standard, Fire Tests of BuildingConstruction and Materials, UL 263 (ASTM E119), 14^(th) Edition datedAug. 5, 2021 and the Standard, Standard Methods of Fire Endurance Testsof Building Construction and Materials CAN/ULC-S101-14, Fifth Edition,dated Dec. 2, 2020. The observations during the fire test are summarizedin Table 2 below.

TABLE 2 Exposed (E) or Un- Test exposed Time, (U) Min SurfaceObservations 0 U The measured velocity across the unexposed surface ofthe test assembly was 0 feet per second. 0 E&U Gas on. 5 E Entireexposed face has turned black. 10 E Exposed side board has turnedgray/white. Paper is burning away, core visible in various spots. 17 EExposed side board joints have started to open (less than½ in.). Uppermost panel exhibiting cracks. 22 E Upper most board joint has opened toabout 1 in., wood studs are visible and flaming. Top and bottom boardsshowing cracks. 26 E Stud pattern visible through boards. 28 E Bottomboard joint has opened to about 1 in. Crack in center of bottom boardhas grown. 33 E Significant flaming at exposed board joints. No exposedside board fall off at this point. 40 E Middle board engulfed in flame.Top board joint opened to more than 1 in. Top board showing significantwaving. No board fall off at this time. 46 E Middle exposed panel hasfallen. Top and bottom still attached. 48 E Middle north side of exposedpanel had fallen. 51 E Top exposed board still attached. Studs visibleat center area and still intact. 54 E Exposed side wood studs havefallen. ½ in. Wallboard paper is charring 60 E Paper on wallboard hadturned fully white. 65 E H-studs showing rippling. 70 E Wallboardshowing rippling in center of assembly. 95 E Majority of top panel ofunclassified board (interior wallboard) has fallen. 130 E Wallboardlayers start to deflect further and pull away. 135 E Second layer ofwallboard, north side has fallen. First laye rof wallboard south sidehas fallen. 145 E Down to third layer of wallboard both north and southside. 159 E&U Gas off, assembly no longer maintained load. All framingand gypsum board except for the outer most unclassified layer and woodstuds had fallen into the furnace.

As shown above, the assembly met the requirements for a 2-1/2 hour (150minutes) load bearing wall. The finish rating is defined as the timenecessary to raise the average temperature measured on the face of thewood studs nearest the fire by 250° F. or the time required to raise thetemperature on the wood studs by 325° F. at any point. The averagetemperature measured on the wood studs was 65° F. before the test.Therefore, the average limiting temperature was 315° F. and theindividual limiting temperature was 390° F.

The limiting temperatures for the unexposed surfaces did not occurduring the 159 min. test duration. The average limiting averagetemperature and individual limiting temperatures were 162° F. and 180°F., respectively, at 159 min.

No suspected hot spots developed during the test requiring theapplication of cotton waste or the roving thermocouple.

Next, a duplicate assembly was heated according to the above standardsfor 1 hour prior to a hose stream test. The observations during theheating are summarized in Table 3 below.

TABLE 3 Exposed Test (E) or Time, Unexposed Hr:Min (U) SurfaceObservations 0:00 E/U The measured velocity across the unexposed surfaceof the test assembly was 0 FPS. 1:00 E/U No significant changesoccurred. Gas off.

The assembly was then subjected to the impact, cooling, and erodingaction of a 30 psi water stream applied through a 1-1/8 in. diameternozzle at a distance of 20 ft. for 2-1/2 min. During the hose streamtest, no water penetrated through the 4 layers of ½″ gypsum. boards thatcreated the area separation wall. Also, no water penetrated beyond theunexposed surface during the 2-1/2 minute hose stream test. Instead, theassembly remained intact during the 2-1/2 minute hose stream test.

Although various embodiments have been shown and described, thedisclosure is not limited to such embodiments and will be understood toinclude all modifications and variations as would be apparent to one ofordinary skill in the art. Therefore, it should be understood that thedisclosure is not intended to be limited to the particular formsdisclosed; rather, the intention is to cover all modifications,equivalents, and alternatives falling within the spirit and scope of thedisclosure as defined by the appended claims.

What is claimed is:
 1. A firewall comprising: three or more consecutivelayers of wallboard, and a plurality of fasteners affixing the three ormore layers of the wallboard to one another; wherein each layer of thewallboard comprises gypsum; wherein each layer of the wallboardcomprises a moisture resistant covering on an exterior surface thereof;wherein at least one fastener of the plurality of fasteners is spaced atleast 6″ from horizontal edges of the wallboard and at least 6″ fromvertical edges of the wallboard; and wherein the firewall satisfiesrequirements for a 2-hour load bearing wall under ASTM E119 or UL 263.2. The firewall of claim 1, further comprising metal studs abutting oneor more edges of the wallboard.
 3. The firewall of claim 1, wherein eachlayer of the wallboard further comprises vermiculite and fiber glass. 4.The firewall of claim 1, wherein each of the three or more layers the ofwallboard has a width of 24 to 54 inches and a height of 6 to 16 feet;and wherein the three or more layers of wallboard has a combinedthickness of about 2 inches.
 5. The firewall of claim 1, wherein theplurality of fasteners are laminating screws.
 6. The firewall of claim5, wherein the plurality of fasteners are located on opposite sides ofthe firewall and arranged at regular intervals.
 7. The firewall of claim5, wherein the plurality of fasteners are spaced from one another by adistance of 6 to 24 inches.
 8. The firewall of claim 1, wherein eachlayer of the wallboard comprises gypsum containing stucco at 1300 to1700 parts by weight, vermiculite at 25 to 65 parts by weight, and fiberglass at 3 to 16 parts by weight.
 9. The firewall of claim 8, whereineach layer of the wallboard further comprises an adhesive at 6 to 25parts by weight, a foaming agent at 0.01 to 5 parts by weight, and boricacid at 0.02 to 5 parts by weight.
 10. The firewall of claim 1, whereinthe firewall comprises four or more consecutive layers of wallboard. 11.The firewall of claim 10, wherein plurality of the fasteners are locatedon opposite sides of the firewall and the plurality of fastenerspenetrate through two or three layers of the wallboard.
 12. An areaseparation wall comprising: a pair of interior walls supported onframing and spaced from one another; a firewall positioned within aspace between the pair of interior walls, wherein the firewall compriseswallboard arranged in three or more layers and a plurality of fastenersaffixing the three or more layers of the wallboard to one another,wherein each layer of the wallboard comprises gypsum, wherein each layerof the wallboard comprises a moisture resistant covering on an exteriorsurface thereof, and wherein at least one fastener of the plurality offasteners is spaced at least 6″ from horizontal edges of the wallboardand at least 6″ from vertical edges of the wallboard; and clips affixingthe firewall to the framing; wherein the area separation wall satisfiesthe requirements for a 2-hour load bearing wall under ASTM E119 or UL263.
 13. The area separation wall of claim 12, wherein the pair ofinterior walls are spaced from the firewall by a distance of at leastabout 0.75 inches.
 14. The area separation wall of claim 12, whereineach layer of the wallboard further comprises vermiculite and fiberglass.
 15. The area separation wall of claim 12, wherein each layer ofthe wallboard comprises gypsum-containing stucco at 1300 to 1700 partsby weight, vermiculite at 25 to 65 parts by weight, and fiber glass at 3to 16 parts by weight.
 16. The area separation wall of claim 15, whereineach layer of the wallboard further comprises an adhesive at 6 to 25parts by weight, a foaming agent at 0.01 to 5 parts by weight, and boricacid at 0.02 to 5 parts by weight.